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Thursday, September 25, 2008

A NASA artist imagines the Mars exploration rovers Spirit and Opportunity look like this on the Red Planet.

For well over a century, the prospect of life on Mars has been the subject of feverish speculation among scientists. In 1877, Italian astronomer Giovanni Schiaparelli reported seeing “canali” on Mars through his telescope and thought that the dark areas he noticed on the planet were the result of vegetation. By 1894, Percival Lowell, a wealthy American astronomer, who established the observatory that now bears his name, was asserting that in the Martian canals “we are looking upon the result of the work of some sort of intelligent beings.” What those Martian beings might look like and how they would behave towards neighbours on planet Earth have been the subject of much science fiction writing and films. It is no wonder that humans began sending probes to study the Red Planet almost as soon as the space age began. Just three years after Sputnik went into space in 1957, the Soviet Union attempted to send the Korabl-4 but the probe did not even reach the orbit around the earth. Since then, close to 40 spacecraft have been despatched to Mars, but over 60 per cent of those missions also ended in failure. It was Mariner-4 launched by the United States that sent back the first close-up images of another planet as it flew past Mars in July 1965. Finally, the Viking-1 lander, again from the U.S., touched down safely on its surface in July 1976, and it was followed by the Viking-2 lander a few months later. Both Viking landers were sent to look for signs of life. When the planet appeared to be barren, so great was the disappointment that it eroded political support in the U.S. for further Mars missions.But interest in Martian life has revived. If such life exists — or existed in the past — it is likely to take the form of tiny microbes, not little green men travelling in flying saucers. There was an uproar in 1996 when a team of U.S. scientists reported in the journal Science that a Martian meteorite found in Antarctica carried telltale traces of primitive microbial life. Although that interpretation of the traces found on the rock is now not generally accepted, the possibility of life on Mars is not discounted. Space probes have discovered signs that liquid water was present on the planet in the past and that water in the form of ice is still plentiful below the surface. Where there is water, there may well be microscopic life. The Phoenix Mars Lander, which has landed safely in the far north of the planet, joins three other spacecraft and two robotic rovers that are currently examining Mars in unprecedented detail. The objective is not to look for life, but to determine if the Martian arctic soil could support life. Let us wait and see what it finds.